Recently, there has been rapid development in semiconductor technology and, as a result, semiconductors are becoming smaller, circuitry within semiconductors is becoming increasingly dense to provide higher speeds. As the density increases however, higher power is used in these semiconductor components. Additionally, there is a trend toward combining multiple semiconductors in a single package to form a system-in-a-package or a multi-chip module. As the circuit density increases and multiple semiconductors are placed in one package, heat generation typically increases as well. Thus, heat dissipation is becoming more critical as semiconductor technology develops to address the increasing demand for semiconductors having higher power and speed.
Various techniques may be used to remove or dissipate heat generated by a semiconductor. One such technique involves the use of a mass of conductive material in thermal contact with the semiconductor. The mass of conductive material typically is referred to as a heat spreader. One of the primary purposes of a heat spreader is to absorb and dissipate the heat generated by the electronic circuitry on the semiconductor and to spread the heat away from the semiconductor. The heat spreader thereby removes the heat from the semiconductor and reduces the likelihood of the occurrence of hot spots that can have an adverse effect on the performance and reliability of the semiconductor.
Heat spreaders are made of a thermally conductive material such as aluminum, electro-plated copper, copper alloy, or ceramic, for example. A heat spreader is positioned in thermal contact with a semiconductor by use of a thermally conductive material, such as thermally conductive gels, greases, or solders, as well as to provide thermal conductivity between the semiconductor and the heat spreader.
An electronic device may comprise at least one semiconductor coupled to a heat spreader and a substrate carrier. Passive electronic components such as capacitors also may be attached to the substrate carrier. Typically, the semiconductor is attached to one side of the substrate carrier by means of a number of solder balls, solder bumps, or other alternative connections. The heat spreader may be formed out of a suitable thermally conductive material such as copper, aluminum, carbon composites, or alternative suitable materials. The heat spreader is typically positioned in thermal contact with the semiconductor by means of a thermal adhesive.
Some heat spreaders have a lip around all, or a portion, of the body of the heat spreader. The lip is used to attach the heat spreader to the substrate and to provide structural leg support for the body of the heat spreader around the semiconductor. However, the lip does not contribute significantly to heat dissipation, and may add weight and cost to an electronic device. The lip also occupies space on the substrate that otherwise could be used for placement of additional passive components or semiconductors.
Other heat spreaders have a number of legs that support the body of the heat spreader a distance above the substrate carrier. The distance between the upper surface of the substrate carrier and the lower surface of the body of the heat spreader is referred to herein as the Z-dimension. However, the legs of these heat spreaders utilize substantial portions of the surface area of the substrate carrier that otherwise could be used to carry a larger semiconductor, additional passive components, or additional semiconductors. A need exists for an improved heat spreader design, which does not utilize a significant portion of the substrate carrier for attachment of the heat spreader while maintaining the Z-dimension over the surface of the substrate carrier.
Attaching a heat spreader to the surface of a semiconductor substrate inside of the package often results in solder mask cracking or copper tracer damage during thermal stress testing due to the mismatch of the thermal coefficient of expansion between the heat spreader and the semiconductor substrate.
Additionally, the design of the heat spreader can be very complex resulting in a relatively expensive component for semiconductors that include heat spreaders. The heat spreader to be used also depends upon the size of the semiconductor requiring the manufacture and storage of a variety of sizes of heat spreaders.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.